Automotive internal combustion engines utilize exhaust systems for directing burnt gases out of the engine cylinders and for dampening exhaust noises. Factory-installed exhaust systems typically include an exhaust manifold, an exhaust pipe extending from the exhaust manifold to the rear of the vehicle, a muffler coupled to the end of the exhaust pipe, and a tailpipe extending from the muffler to outside the vehicle. Exhaust manifolds formed of thick cast iron and high-restriction mufflers are installed at the factory to achieve substantial sound dampening. The drawback to these manifolds and mufflers is that they severely impair the flow of exhaust gases, which greatly reduces the power output of the engine, and add weight, which decreases performance and increases gas consumption.
To increase engine efficiency and performance, the exhaust system can be replaced with commercially available low-restriction manifolds and mufflers that more effectively exhaust burnt gases without significantly increasing the exhaust noise. Low-restriction manifolds, typically referred to as "headers", have equal length, lightweight, large diameter tubes tuned to a predetermined resonant frequency that scavenge the burnt gases from the engine with a high amount of efficiency. In addition, these headers maintain exhaust noise at a minimum level and cool the engine by quickly dissipating heat. Low-restriction mufflers further reduce back pressure while producing a pleasing sound. To further reduce back pressure and lower exhaust noises, it has been found that a balance tube installed between the two exhaust pipes on a V-8 engine will balance out the flow of burnt gases and dampen low-frequency sound pulses.
Owners of some foreign cars have found it desirable to exchange the heavy, low-performance foreign engine for a lighter, high-performance American engine. A popular exchange is a domestic V-8 engine, such as a small-block Chevrolet engine, into a foreign sports car, such as a 911 S Porsche automobile. Because these engine exchanges are not done on a large scale, preformed exhaust systems for these engine-body combinations are not commercially available. As a result, the exhaust system must be custom-fabricated. Because foreign automobiles are not designed to accept domestic engines, a number of difficulties are encountered in fabricating the exhaust system. For instance, because a V-8 engine mounted in the 911 S Porsche faces rearward, the exhaust manifold will direct the exhaust gases in a forward direction. Furthermore, the combination transmission and drive axle, commonly referred to as a "transaxle", interferes with the routing of exhaust pipes and prevents the use of headers and balance tubes. As a result, the exhaust system must be configured to curve ahead of the transaxle to redirect the exhaust gases toward the rear of the automobile. Consequently, the exhaust system on these engine exchanges uses a complex arrangement of exhaust pipes without the benefit of headers and balance tubes that results in a loud sound with poor performance from the engine.